Add package-config tests where test is running in Isolate.spawn-isolates.

tests/standalone/standalone.status

 # Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # WARNING:
 # Tests using the multitest feature where failure is expected should *also* be
 # listed in tests/lib/analyzer/analyze_tests.status without the "standalone"
 # prefix.
 
+packages_file_test: Slow
+
 package/invalid_uri_test: Fail, OK # CompileTimeErrors intentionally
 package/scenarios/packages_file_strange_formatting/empty_package_dir_test: Fail, OK # CompileTimeErrors intentionally
 package/scenarios/empty_packages_file/empty_packages_file_discovery_test: Fail, OK # CompileTimeErrors intentionally
 package/scenarios/empty_packages_file/empty_packages_file_option_test: Fail, OK # CompileTimeErrors intentionally
 package/scenarios/invalid/invalid_package_name_test: RuntimeError, CompileTimeError # Errors intentionally
 package/scenarios/invalid/same_package_twice_test.dart: RuntimeError, CompileTimeError # Errors intentionally
 full_coverage_test: Pass, Slow, Timeout
 verified_mem_test: Pass, Slow, Timeout # Does verify before and after GC.
 
 issue14236_test: Pass # Do not remove this line. It serves as a marker for Issue 14516 comment #4.
@@ skipping 286 matching lines @@
 
 [ $compiler == precompiler && $runtime == dart_precompiled && $system == android ]
 io/*: Skip # Issue #26376
 
 typed_data_isolate_test: Skip # Issue #26376
 typed_array_test: Skip # Issue #26376
 typed_array_int64_uint64_test: Skip # Issue #26376
 
 oom_error_stacktrace_test: Skip # Issue #26377
 out_of_memory_test: Skip # Issue #26377